graveyard vs potter's field

graveyard

noun
  • A tract of land in which the dead are buried. 

  • The discard pile, in some trading card games. 

  • A team where players are sent when they are not useful, or a team where players become useless if sent there. 

  • Synonym of suicide (“beverage combining all available flavors at a soda fountain”) 

potter's field

noun
  • A public place where strangers, paupers, and criminals are buried. 

How often have the words graveyard and potter's field occurred in a corpus of books? (source: Google Ngram Viewer )